Engine flush process and composition

ABSTRACT

An internal combustion engine can be cleaned of sludge, deposits, or wear debris, by supplying to lubricated surfaces of said engine a composition having a kinematic viscosity of 1 to 10 mm 2 /s at 100° C. comprising oil having at least 15% aromatics by ASTM D-2007; at least 2.5 weight percent of a nitrogen-containing dispersant; at least 0.6 weight percent of an overbased metal detergent; and at least about 0.5 weight percent of a metal salt of a phosphorus acid, circulating the composition through the engine and removing the composition from the engine.

BACKGROUND OF THE INVENTION

The present invention relates to a composition and process suitable for flushing an internal combustion engine to remove sludge, deposits, or wear from lubricated surfaces of the engine.

There is a need to develop an engine flush lubricant to clean older engines, typically those with greater than 120,000 km (75,000 mi.) on the odometer. Among the devices known to be used for supplying cleaning fluids to engines are those described in U.S. Pat. No. 5,460,656, among others. There are, indeed, numerous engine cleaning or flushing compositions available for use, many of which may contain kerosene, mineral spirits, or other solvents. It is believed that typical engine flush oils may sometimes contain 60-98% kerosene (also known as Fuel Oil No. 1) or diesel fuel No. 2; 1-15% solvents or light base stocks such as ethylene glycol monobutyl ether, 2-ethyoxyethanol, solvent dewaxed heavy paraffinic petroleum distillates (the foregoing may sometimes be present at 75% or more), hydrotreated heavy naphthenic petroleum distillates, and heavy aromatic petroleum solvent naphtha. These materials can be volatile or flammable or both, as well as difficult to store and dispose of. Conventional solvent based flush systems, moreover, typically do nothing to recondition the surfaces of a cleaned engine.

An engine flush oil from The Valvoline Company is reported on an MSDS dated Jan. 14, 2002 as containing 85.0-95.0% by volume kerosene, 0.0-10.0% aromatic petroleum distillates, 0.0-9.0% ethylene glycol monobutyl ether, and 0.0-7.0% diacetone alcohol (available at http://msds.ashland.com). An “oil system cleaner” [as apparently distinguished from a “complete oil system flush” also offered] from Gold Eagle Company, “VS7,” is reported on an MSDS dated May 14, 2003 as containing refined petroleum oil and having a flash point >93.3C. An internet web site (http://www.mightyautoparts.com/products/products_vs7_oil.html, accessed Nov. 1, 2004) states that the VS7 oil system cleaner does not contain oil-thinning kerosene or mineral spirits.

The present invention, therefore, solves the problem of providing an effective engine flush lubricant which can be free from volatile, flammable solvents and which serves to condition engine parts.

SUMMARY OF THE INVENTION

The present invention provides a method for removing at least a portion of at least one of sludge, deposits, and wear debris from the lubricated surfaces of an internal combustion engine which has accumulated such sludge, deposits, or wear debris, comprising:

(a) supplying to lubricated surfaces of said engine a composition having a kinematic viscosity of 1 to 9.3 mm²/s at 100° C. and a flash point of at least about 125° C., comprising

-   -   (i) oil having at least 15% aromatics by ASTM D-2007;     -   (ii) at least 2.5 weight percent of a nitrogen-containing         dispersant; and     -   (iii) at least 0.6 weight percent of an overbased metal         detergent;

(b) circulating said composition through the engine; and

(c) removing said composition from the engine.

The invention further provides a cleaning composition for an engine, comprising the components as described above.

DETAILED DESCRIPTION OF THE INVENTION

Various preferred features and embodiments will be described below by way of non-limiting illustration.

The composition employed in the present invention includes an oil having at least 15% aromatics by ASTM D-2007; at least about 2.5 weight percent of a nitrogen-containing dispersant; at least about 0.6 weight percent of an overbased metal detergent; and at least about 0.5 weight percent of a zinc dihydrocarbyldithiophosphate.

The oil comprises the major portion of the composition used for flushing, cleaning, and conditioning the engine. It is typically a mineral oil, although other types of oils such as animal oils, vegetable oils, or synthetic oils such as esters, polyalphaolefins, or oils from hydroisomerization of waxes such as Fischer-Tropsch materials, can also be used. This will be an oil having a kinematic viscosity suitable to provide a viscosity of the entire composition of of 1 to 9.3 mm²/s (cSt) at 100° C., or alternatively 2 to 8 or 2.5 to 6 mm²/s. This viscosity represents of the overall composition corresponds generally to a viscosity of the oil itself, apart from the influence of any additives, of perhaps 0.5 to 7.5 or 1 to 6 or 1 to 5 or 1.4 or 2 to 4.5 mm²/s at 100° C. If multiple individual oils are employed, the mixture of oils will have the designated viscosity.

The oil should have a significant content of aromatic component. It is believed that oils having a relatively high aromatics content will exhibit superior solvent properties for certain engine surface contaminants, leading to more efficient cleaning. Aromatics can be determined by ASTM D-2007, and represents the amount of aromatic content of the oil. The aromatic content of the oil should be at least 15%; alternatively expressed, the oil should have less than 85% saturates, assuming that the amount of polar compounds in the oil is negligible. (Aromatics+saturates+polar compounds=100% by ASTM D-2007.) In alternative embodiments, the oil can have 17 to 50% or 20 to 40% aromatics. If a mixture of oils is used, the mixture should have the above-described aromatics content. Base oils are commonly characterized in terms of aromatics content or saturates content, so this information will generally be readily available for any given oil. Mineral oils having high aromatics content and thus a high level of unsaturates will typically be included within the API Group I classification of base oils or base stocks. Group I is defined as oils containing more than 0.03% sulfur and/or less than 90% saturates, and having a viscosity index of 80 to 120. The oil can also contain a certain minor amount of other grade oils such as synthetic esters, e.g., up to about 15 percent by weight.

The amount of the oil will typically be the total of the composition less the amounts of the required and optional additives, as described below. In certain embodiments the amount of oil can be 75 to 98 percent or 80 to 96 percent or 85 to 94 percent by weight of the total formulation. It is noted that many of the additives commonly used may themselves be customarily provided as solutions in diluent oil. The amount of diluent oil provided along with the additives, for calculation purposes, is included in the total amounts of oil as recited above. The properties of the oil, in terms of viscosity and aromatics content, should be interpreted to be those of the entire oil component, including contribution from diluent oil of the additives.

The formulation in certain embodiments will contain little or no volatile or flammable solvents. Typical solvents which may be avoided include those having a flash point (D-92) of less than 93° C. (200° F) or less than 90° C. or less than 80° C., or alternatively less than 100° C. or 120° C. or 150° C. Typical solvents which may be avoided can also include materials which have a normal boiling point of less than 325° C. or 290° C. or 175° C. or 165° C. or 135° C. Such materials which may be avoided if desired include kerosene (flash point 81° C., boiling point 175-325° C.) and Cellosolve (2-ethoxyethanol, flash point 44° C., boiling point 135° C.) as well as aromatic solvents such as toluene and xylene and aliphatic hydrocarbon solvents such as mineral spirits. Other solvents which may be avoided if desired include ketones such as acetone or methyl ethyl ketone and ethers such as 2-butoxyethanol (flash point 60° C., boiling point 171° C. at 99 kPa) as well as aromatic distillates in the range of C9 through C16, boiling in the range of 165° C. to 290° C. The amount of such solvents in the formulation can be less than 5% or 3% or 1% or 0.5% or 0.1% by weight. In one embodiment, the formulation is substantially free from volatile or flammable solvents. The amounts can also be limited in such a way that the flash point of the composition as a whole is greater than 125° C. or greater than 130 or 150 or 180 or 200 or even 210° C.; typically a mineral oil-based composition will have a flash point of 130 or 135 or 165 up to 300 or 260° C.; certain synthetic compositions may have a yet higher flash point.

Other materials present in the composition used in the present invention include materials which can serve to condition the lubricated surfaces. Such materials or additives include nitrogen containing dispersant, overbased metal detergent, and zinc dihydrocarbyldithiophosphate.

Nitrogen-containing dispersants are well known in the lubricant industry and include many of what are known as ashless-type dispersants. Ashless type dispersants are characterized by a polar group attached to a relatively high molecular weight hydrocarbon chain. Typical nitrogen-containing ashless dispersants include N-substituted long chain alkenyl succinimides, having a variety of chemical structures including typically

where each R¹ is independently an alkyl group (which may bear more than one succinimide group, by various methods of attachment), frequently a polyisobutyl group with a molecular weight of 500-5000, and R² are alkylene groups, commonly ethylene (C₂H₄) groups. Such molecules are commonly derived from reaction of an alkenyl acylating agent with a polyamine, and a wide variety of linkages between the two moieties is possible beside the simple imide structure shown above, including a variety of amides and quaternary ammonium salts. Succinimide dispersants are more fully described in U.S. Pat. Nos. 4,234,435 and 3,172,892. Additionall succinimide dispersants are those having a N:CO ratio of greater than about 1:1, that is, with overall excess nitrogen functionality derived from the polyamine, compared with the carbonyl functionality derived from the succinic acid groups. Such materials may also be described as high nitrogen dispersants, containing at least 1.6% or at least 2% nitrogen in the dispersant (on an active chemical, oil-free basis) and having a relatively high total base number (TBN) of at least 30, 40, or even 50 (mg equivalent KOH per gram of sample, active chemical basis). Suitable ranges of TBN can include 5-60 or 15-45. In certain embodiments, the TBN of the dispersant is less than 45 or less than 40 or less than 30. In certain embodiments, the total acid number (TAN) is at least 4 or 5. The TAN can be, for instance 4 or 5 to 20 or to 10. Useful materials also include relatively high molecular weight dispersants, having, for instance alkyl or hydrocarbyl (polymer) groups with {overscore (Mn)} of greater than 1300.

Another class of nitrogen-containing dispersant is Mannich bases. These are materials which are formed by the condensation of a higher molecular weight, alkyl substituted phenol, an alkylene polyamine, and an aldehyde such as formaldehyde. Such materials may have the general structure

(including a variety of isomers and the like) and are described in more detail in U.S. Pat. No. 3,634,515.

Other nitrogen-containing dispersants include polymeric dispersant additives, which are generally hydrocarbon-based polymers which contain nitrogen-containing polar functionality, such as succinimide functionality, as described above, to impart dispersancy characteristics to the polymer.

Dispersants can also be post-treated by reaction with any of a variety of agents. Among these are urea, thiourea, dimercaptothiadiazoles, carbon disulfide, aldehydes, ketones, carboxylic acids, hydrocarbon-substituted succinic anhydrides, nitrites, epoxides, boron compounds, and phosphorus compounds. References detailing such treatment are listed in U.S. Pat. No. 4,654,403.

The nitrogen-containing dispersant will be present in the composition of the present invention in an amount of at least 2.5 weight percent, or 2.7 to 8 weight percent, or 3 to 7 weight percent. Either a single dispersant or multiple dispersants can be present.

The composition of the present invention will also contain one or more metal-containing detergents. Metal-containing detergents are typically overbased materials, or overbased detergents. Overbased materials, otherwise referred to as overbased or superbased salts, are generally homogeneous Newtonian systems characterized by a metal content in excess of that which would be present for neutralization according to the stoichiometry of the metal and the particular acidic organic compound reacted with the metal. The overbased materials are prepared by reacting an acidic material (typically an inorganic acid or lower carboxylic acid, preferably carbon dioxide) with a mixture comprising an acidic organic compound, a reaction medium comprising at least one inert, organic solvent (e.g., mineral oil, naphtha, toluene, xylene) for said acidic organic material, a stoichiometric excess of a metal base, and a promoter such as a phenol or alcohol and optionally ammonia. The acidic organic material will normally have a sufficient number of carbon atoms, for instance, as a hydrocarbyl substituent, to provide a reasonable degree of solubility in oil. The amount of excess metal is commonly expressed in terms of metal ratio. The term “metal ratio” is the ratio of the total equivalents of the metal to the equivalents of the acidic organic compound. A neutral metal salt has a metal ratio of one. A salt having 4.5 times as much metal as present in a normal salt will have metal excess of 3.5 equivalents, or a ratio of 4.5.

Overbased detergents are often characterized by Total Base Number (TBN). TBN is the amount of strong acid (perchloric or hydrochloric) needed to neutralize all of the overbased material's basicity, expressed as potassium hydroxide equivalents (mg KOH per gram of sample). Since overbased detergents are commonly provided in a form which contains a certain amount of diluent oil, for example, 40-50% oil, the actual TBN value for such a detergent will depend on the amount of such diluent oil present, irrespective of the “inherent” basicity of the overbased material. For the purposes of the present invention, the TBN of an overbased detergent is to be recalculated to an oil-free basis. Thus, for instance, a detergent composition having an uncorrected TBN of 300 and 40% oil content could have a TBN (oil-free basis) of 500. Detergents which are useful in the present invention typically have a TBN (oil-free basis) of 100 to 800, and in one embodiment 150 to 750, and in another, 400 to 700. If multiple detergents are employed, the overall TBN of the detergent component (that is, an average of all the specific detergents together) will typically be in the above ranges.

The overall TBN of the composition, including oil, will derived from the TBN contribution of the individual components, such as the dispersant, the detergent, and other basic materials. The overall TBN will typically be at least 7 or at least 10, or sometimes even at least 20. The majority of the TBN is typically contributed by the overbased detergent component. In certain embodiments which include a sodium sulfonate detergent, the TBN contribution form the sodium sulfonate detergent can be at least 2 or at least 3. Sulfated ash (ASTM D-874) is another parameter often used to characterize such compositions. Certain of the compositions of the present invention can have sulfated ash levels of 0.5 to 5% or 0.8 to 4% or to 2%, for instance, greater than 0.8%, greater than 1.0%, or even greater than 2%.

The metal compounds useful in making the basic metal salts are generally any Group 1 or Group 2 metal compounds (CAS version of the Periodic Table of the Elements). The Group 1 metals of the metal compound include Group 1a alkali metals such as sodium, potassium, and lithium, as well as Group 1b metals such as copper. The Group 1 metals can be sodium, potassium, lithium and copper, and in one embodiment sodium or potassium, and in another embodiment, sodium. The Group 2 metals of the metal base include the Group 2a alkaline earth metals such as magnesium, calcium, and barium, as well as the Group 2b metals such as zinc or cadmium. In one embodiment the Group 2 metals are magnesium, calcium, barium, or zinc, and in another embodiments magnesium or calcium. In certain embodiments the metal is calcium or sodium or a mixture of calcium and sodium. Generally the metal compounds are delivered as metal salts. The anionic portion of the salt can be hydroxide, oxide, carbonate, borate, or nitrate.

Such overbased materials are well known to those skilled in the art. Patents describing techniques for making basic salts of sulfonic acids, carboxylic acids, (hydrocarbyl-substituted) phenols, phosphonic acids, and mixtures of any two or more of these include U.S. Pat. Nos. 2,501,731; 2,616,905; 2,616,911; 2,616,925; 2,777,874; 3,256,186; 3,384,585; 3,365,396; 3,320,162; 3,318,809; 3,488,284; and 3,629,109.

In one embodiment the lubricants of the present invention can contain an overbased sulfonate detergent. Suitable sulfonic acids include sulfonic and thiosulfonic acids. Sulfonic acids include the mono- or poly-nuclear aromatic or cycloaliphatic compounds. Oil-soluble sulfonates can be represented for the most part by one of the following formulas: R₂-T-(SO₃ ⁻)_(a) and R₃—(SO₃ ⁻)_(b), where T is a cyclic nucleus such as typically benzene; R₂ is an aliphatic group such as alkyl, alkenyl, alkoxy, or alkoxyalkyl; (R₂)-T typically contains a total of at least about 15 carbon atoms; and R₃ is an aliphatic hydrocarbyl group typically containing at least 15 carbon atoms. Examples of R₃ are alkyl, alkenyl, alkoxyalkyl, and carboalkoxyalkyl groups. The groups T, R₂, and R₃ in the above formulas can also contain other inorganic or organic substituents in addition to those enumerated above such as, for example, hydroxy, mercapto, halogen, nitro, amino, nitroso, sulfide, or disulfide. In the above formulas, a and b are at least 1.

Another overbased material which can be present is an overbased phenate detergent. The phenols useful in making phenate detergents can be represented by the formula (R₁)_(a)—Ar—(OH)_(b), wherein R₁ is an aliphatic hydrocarbyl group of 4 to 400 carbon atoms, or 6 to 80 or 6 to 30 or 8 to 25 or 8 to 15 carbon atoms; Ar is an aromatic group (which can be a benzene group or another aromatic group such as naphthalene); a and b are independently numbers of at least one, the sum of a and b being in the range of two up to the number of displaceable hydrogens on the aromatic nucleus or nuclei of Ar. In one embodiment, a and b are independently numbers in the range of 1 to 4, or 1 to 2. R₁ and a are typically such that there is an average of at least 8 aliphatic carbon atoms provided by the R₁ groups for each phenol compound. Phenate detergents are also sometimes provided as sulfur-bridged species.

Another detergent can be a salicylate detergent. The alkylsalicylate can be an alkali metal salt or an alkaline earth metal salt of an alkylsalicylic acid which can in turn be prepared from an alkylphenol by Kolbe-Schmitt reaction. The alkylphenol can be prepared by a reaction of α-olefin having 8 to 30 carbon atoms (mean number) with phenol. Alternatively, calcium salicylate can be produced by direct neutralization of alkylphenol and subsequent carbonation.

In one embodiment, the overbased material is an overbased detergent selected from the group consisting of overbased salixarate detergents, overbased saligenin detergents, overbased salicylate detergents, and overbased glyoxylate detergents, and mixtures thereof. Overbased saligenin detergents are commonly overbased magnesium salts which are based on saligenin derivatives. A general example of such a saligenin derivative can be represented by the formula

wherein X comprises —CHO or —CH₂OH, Y comprises —CH₂— or —CH₂OCH₂—, and wherein such —CHO groups typically comprise at least 10 mole percent of the X and Y groups; M is hydrogen, ammonium, or a valence of a metal ion, R¹ is a hydrocarbyl group containing 1 to 60 carbon atoms, m is 0 to typically 10, and each p is independently 0, 1, 2, or 3, provided that at least one aromatic ring contains an R¹ substituent and that the total number of carbon atoms in all R¹ groups is at least 7. When m is 1 or greater, one of the X groups can be hydrogen. In one embodiment, M is a valence of a Mg ion or a mixture of Mg and hydrogen. Other metals include alkali metals such as lithium, sodium, or potassium; alkaline earth metals such as calcium or barium; and other metals such as copper, zinc, and tin.

As used herein, the expression “represented by the formula” indicates that the formula presented is generally representative of the structure of the chemical in question. However, it is well known that minor variations can occur, including in particular positional isomerization, that is, location of the X, Y, and R groups at different position on the aromatic ring from those shown in the structure. The expression “represented by the formula” is expressly intended to encompass such variations.

Saligenin detergents are disclosed in greater detail in U.S. Pat. No. 6,310,009, with special reference to their methods of synthesis (Column 8 and Example 1) and preferred amounts of the various species of X and Y (Column 6).

Salixarate detergents are overbased materials that can be represented by a substantially linear compound comprising at least one unit of formula (I) or formula (II):

each end of the compound having a terminal group of formula (III) or (IV):

such groups being linked by divalent bridging groups A, which may be the same or different for each linkage; wherein in formulas (I)-(IV) R³ is hydrogen or a hydrocarbyl group; R² is hydroxyl or a hydrocarbyl group and j is 0, 1, or 2; R⁶ is hydrogen, a hydrocarbyl group, or a hetero-substituted hydrocarbyl group; either R⁴ is hydroxyl and R⁵ and R⁷ are independently either hydrogen, a hydrocarbyl group, or hetero-substituted hydrocarbyl group, or else R⁵ and R⁷ are both hydroxyl and R⁴ is hydrogen, a hydrocarbyl group, or a hetero-substituted hydrocarbyl group; provided that at least one of R⁴, R⁵, R⁶ and R⁷ is hydrocarbyl containing at least 8 carbon atoms; and wherein the molecules on average contain at least one of unit (I) or (III) and at least one of unit (II) or (IV) and the ratio of the total number of units (I) and (III) to the total number of units of (II) and (IV) in the composition is about 0.1:1 to about 2:1. The divalent bridging group “A,” which may be the same or different in each occurrence, includes —CH₂— (methylene bridge) and —CH₂OCH₂— (ether bridge), either of which may be derived from formaldehyde or a formaldehyde equivalent (e.g., paraform, formalin).

Salixarate derivatives and methods of their preparation are described in greater detail in U.S. Pat. No. 6,200,936 and PCT Publication WO 01/56968. It is believed that the salixarate derivatives have a predominantly linear, rather than macrocyclic, structure, although both structures are intended to be encompassed by the term “salixarate.”

Glyoxylate detergents are similar overbased materials which are based on an anionic group which, in one embodiment, may have the structure

wherein each R is independently an alkyl group containing at least 4, and preferably at least 8 carbon atoms, provided that the total number of carbon atoms in all such R groups is at least 12, preferably at least 16 or 24. Alternatively, each R can be an olefin polymer substituent. The acidic material upon from which the overbased glyoxylate detergent is prepared is the condensation product of a hydroxyaromatic material such as a hydrocarbyl-substituted phenol with a carboxylic reactant such as glyoxylic acid and other omega-oxoalkanoic acids. Overbased glyoxylic detergents and their methods of preparation are disclosed in greater detail in U.S. Pat. No. 6,310,011 and references cited therein.

The overbased detergent can also be an overbased salicylate. The salicylic acids preferably are hydrocarbyl-substituted salicylic acids, preferably aliphatic hydrocarbon-substituted salicylic acids wherein each substituent contains an average of at least 8 carbon atoms per substituent and 1 to 3 substituents per molecule. The substituents can be polyalkene substituents, where polyalkenes include homopolymers and interpolymers of polymerizable olefin monomers of 2 to about 16, preferably 2 to 6, or 2 to 4 carbon atoms. The olefins may be monoolefins such as ethylene, propylene, 1-butene, isobutene, and 1-octene; or a polyolefinic monomer, such as diolefinic monomer, such 1,3-butadiene and isoprene. In one embodiment, the hydrocarbyl substituent group or groups on the salicylic acid contains 7 to 300 carbon atoms and can be an alkyl group having a molecular weight of 150 to 2000. The polyalkenes and polyalkyl groups are prepared by conventional procedures, and substitution of such groups onto salicylic acid can be effected by known methods. Overbased salicylate detergents and their methods of preparation are disclosed in U.S. Pat. Nos. 4,719,023 and 3,372,116.

Other overbased detergents can include overbased detergents having a Mannich base structure, as disclosed in U.S. Pat. No. 6,569,818.

The amount of the overbased detergent, in the formulations of the present invention, is typically at least 0.6 weight percent on an oil-free basis. In other embodiments, it can be present in amounts of 0.7 to 5 weight percent or 1 to 3 weight percent. Either a single detergent or multiple detergents can be present.

The formulation of the present invention will optionally also contain a metal salt of a phosphorus acid, especially of a sulfur-containing phosphoric acid. Metal salts of the formula

wherein R⁸ and R⁹ are independently hydrocarbyl groups containing 3 to 30 carbon atoms are readily obtainable by the reaction of phosphorus pentasulfide and an alcohol or phenol to form an O,O-dihydrocarbyl phosphorodithioic acid corresponding to the formula

The reaction typically involves mixing at a temperature of 20° C. to 200° C., four moles of an alcohol or a phenol with one mole of phosphorus pentasulfide. Hydrogen sulfide is liberated in this reaction. The acid is then reacted with a basic metal compound to form the salt. The metal M, having a valence n, generally is aluminum, lead, tin, manganese, cobalt, nickel, zinc, or copper, and most preferably zinc. The basic metal compound is often zinc oxide, thus typically forming a zinc dihydrocarbyldithiophosphate (ZDDP), and the resulting metal compound is represented by the formula

The R⁸ and R⁹ groups are independently hydrocarbyl groups that are typically free from acetylenic and often also from ethylenic unsaturation. They are typically alkyl, cycloalkyl, aralkyl or alkaryl group and have 3 to 20 carbon atoms, for instance, 3 to 16 carbon atoms or up to 13 carbon atoms, e.g., 3 to 12 carbon atoms. The alcohol which reacts to provide the R⁸ and R⁹ groups can be a mixture of a secondary alcohol and a primary alcohol, for instance, a mixture of isopropanol and 4-methyl-2-pentanol. Such materials are often referred to as zinc dialkyldithiophosphates or simply zinc dithiophosphates. They are well known and readily available to those skilled in the art of lubricant formulation.

The amount of the metal salt of a phosphorus acid will typically be at least 0.5 percent by weight, and in certain embodiments 0.6 to 3 percent by weight or 0.7 to 2 percent by weight. Either a single salt (e.g., ZDDP) or multiple salts may be present.

The composition used in the present invention may optionally contain one or more additional additives which are commonly found in engine lubricants. Such materials can include antioxidants, seal swell agents, friction modifiers, pour point depressants, viscosity modifiers, fluidizing agents, corrosion inhibitors, rust inhibitors, and anti-foam agents.

Antioxidants include aromatic amines such as those of the formula

wherein R⁵ is a phenyl group or a phenyl group substituted by R⁷, and R⁶ and R⁷ independently a hydrogen or an alkyl group containing 1 to 24 carbon atoms. In one embodiment R⁵ is a phenyl group substituted by R⁷ and R⁶ and R⁷ are alkyl groups containing 4 to 20 carbon atoms. In one embodiment, the amine antioxidant comprises dinonyldiphenylamine as may be represented by

or alternatively a mixture of nonyl- and dinonyldiphenylamine.

Antioxidants also include hindered alkyl phenols represented by the formula

wherein R⁴ is an alkyl group containing 1 to 24 carbon atoms and a is an integer of 1 to 5, such as 2, and the substituents being in the ortho positions to the OH group. In one embodiment, a hindered phenol can contain t-butyl groups and can be represented by

In other embodiments the para position can be occupied by an alkyl group or by a group linking two such phenolic groups. In yet another embodiment the para position can be the site of an ester group. Such hindered phenol esters are disclosed in U.S. Pat. No. 6,559,105, and can be represented by

wherein R³ is an alkyl group; in certain embodiments the alkyl group can contain containing 2 to 6 carbon atoms or preferably 2 to 4 carbon atoms or 4 carbon atoms (e.g., an n-butyl group). In other embodiments R³ can contain 6 or 8 to 30 carbon atoms.

Other antioxidants include reaction products of a sulfur source and a Diels-Alder adduct, which in turn can be prepared from a dienophile having a carboxylic ester group. The antioxidant component, if present can be present, for example, in an amount of about 1%, for instance, 0-3%, 0.1-2%, or 0.5 to 1.5% by weight.

Seal swell agents include sulfolanes such as isodecyl sulfolane, or alternatively phthalate esters, which are designed to keep seals pliable. Sulfolanes may, in one embodiment, be represented by the general formula

where R¹ is a hydrocarbon radical having at least 4 carbon atoms and each of R² and R³ is independently hydrogen or a lower alkyl radical, i.e., containing 1 to 7 carbon atoms. In one embodiment R and R³ are both hydrogen. R¹ typically contains 1 to 100 carbon atoms, or 4 to 25 or 6 to 10 carbon atoms. Other seal swell agents include benzyl esters, lactones, and nitriles, and specifically materials such as decanolactone, isodecyl-(bicycloheptyl carboxylactone)-carboxylate, benzyl butyl phthalate, benzyl C₉-C₁₁ alkyl phthalate, and 3-decyloxypropionitrile. Such materials are known from U.S. Pat. No. 4,029,587. The seal swell agent, if present, can be present, for example, in an amount of 0-2% or 0.01-1% or 0.05-2% or 0.1-1%.

Friction modifiers are well known and include many materials that are disclosed, for instance in U.S. Pat. No. 6,528,458 and references cited therein. Some friction modifiers include fatty phosphites, fatty acid amides, fatty epoxides, borated fatty epoxides, fatty amines, glycerol esters (e.g., glycerol monooleate), borated glycerol esters, alkoxylated fatty amines, borated alkoxylated fatty amines, metal salts of fatty acids, sulfurized olefins, fatty imidazolines, condensation products of carboxylic acids and polyalkylene-polyamines, metal salts of alkyl salicylates, and amine salts of alkylphosphoric acids. Among the friction modifiers of interest are organic borate esters. Organic borate esters include esters of alcohols plus a boron source such as boric acid. One species of organic borate ester is the so-called borated epoxides, which are esters formed from the reaction of a boron source plus an organic peroxide, typically to form a cyclic or polymeric structure. The friction modifier, if present, can be present, for example, in an amount of 0.1 to 3 percent by weight or 0.15 to 2 or to 1 percent.

Certain borate esters, depending on length of the alkyl chain(s) can function primarily as corrosion inhibitors rather than friction modifiers. This is particularly true of borate esters having relatively short alkyl chains such as less than C12, e.g., C6 to C10, or about C8, chains. Such materials are described in greater detail in U.S. Pat. No. 6,605,572, see columns 6-7. Examples of such borate esters include the reaction product of boric acid with 2-ethylhexyl alcohol or with alcohols to provide alkyl groups such as isopropyl, n-butyl, isobutyl, amyl, 4-methyl-2-pentyl, isooctyl, decyl, dodecyl, tetracyl, or phenyl. Typical amounts of these or other materials useful as corrosion inhibitors can be 0.1 to 1 percent, or 0.2 to 0.8 percent, or 0.3 to 0.5 or to 0.6 percent

Pour point depressants are another useful type of additive. These can comprise substances such as polymethacrylates, styrene-based polymers, crosslinked alkyl phenols, or alkyl naphthalenes which are useful for reducing the pour point (the temperature at which an oil becomes resistant to pouring) of an oil based composition or lubricant. See for example, page 8 of “Lubricant Additives” by C. V. Smalheer and R. Kennedy Smith (Lesius-Hiles Company Publishers, Cleveland, Ohio, 1967).The pour point depressant, if present, can be present, for example, in an amount of 0.05 to 0.7 weight percent.

Viscosity modifiers are well known materials, generally polymers such as ethylene-propylene copolymers, (meth)acrylic ester polymers, or styrene- and ester-containing copolymers. Viscosity materials such as can be present, if desired, which may increase the 100° C. viscosity of the blend somewhat, while also permitting control or modification of low temperature viscosity. However, the low temperature viscosity of the present formulation may be less critical than that for a conventional lubricant oil, since it is not contemplated that the present formulation will normally be used under very low temperature conditions. Thus, viscosity modifiers may be present at 4% by weight or less, e.g., 0 to 4%, or 0.1 to 2%, or 0.5 to 1%. In one embodiment the composition is substantially free from viscosity modifier, that is, its amount is about 0% or no more than 0.4% or 0.2% or 0.1% or 0.05%.

As used herein, the term “hydrocarbyl substituent” or “hydrocarbyl group” is used in its ordinary sense, which is well-known to those skilled in the art. Specifically, it refers to a group having a carbon atom directly attached to the remainder of the molecule and having predominantly hydrocarbon character. Examples of hydrocarbyl groups include:

hydrocarbon substituents, that is, aliphatic (e.g., alkyl or alkenyl), alicyclic (e.g., cycloalkyl, cycloalkenyl) substituents, and aromatic-, aliphatic-, and alicyclic-substituted aromatic substituents, as well as cyclic substituents wherein the ring is completed through another portion of the molecule (e.g., two substituents together form a ring);

substituted hydrocarbon substituents, that is, substituents containing non-hydrocarbon groups which, in the context of this invention, do not alter the predominantly hydrocarbon nature of the substituent (e.g., halo (especially chloro and fluoro), hydroxy, alkoxy, mercapto, alkylmercapto, nitro, nitroso, and sulfoxy);

hetero substituents, that is, substituents which, while having a predominantly hydrocarbon character, in the context of this invention, contain other than carbon in a ring or chain otherwise composed of carbon atoms. Heteroatoms include sulfur, oxygen, nitrogen, and encompass substituents as pyridyl, furyl, thienyl and imidazolyl. In general, no more than two, preferably no more than one, non-hydrocarbon substituent will be present for every ten carbon atoms in the hydrocarbyl group; typically, there will be no non-hydrocarbon substituents in the hydrocarbyl group.

It is known that some of the materials described above may interact in the final formulation, so that the components of the final formulation may be different from those that are initially added. For instance, metal ions (of, e.g., a detergent) can migrate to other acidic or anionic sites of other molecules. The products formed thereby, including the products formed upon employing the composition of the present invention in its intended use, may not be susceptible of easy description. Nevertheless, all such modifications and reaction products are included within the scope of the present invention; the present invention encompasses the composition prepared by admixing the components described above.

The composition as described above is used to flush or clean an engine, which can be a gasoline, diesel, or natural gas engine, spark ignited or compression ignited, operating on a 4-stroke cycle, and being sump lubricated or otherwise lubricated. The composition is particularly suitable for cleaning a 4-stroke gasoline (spark-ignited) engine which is sump lubricated, or a light duty diesel engine (e.g., for passenger cars).

The method of flushing and cleaning such an engine will comprise the steps of circulating said composition through the engine, that is, typically through some or all of those portions of the engine that are normally exposed to or lubricated by the engine lubricant; and removing the composition from the engine, along with whatever sludge, deposits, wear debris and residual used or contaminated motor oil may be removed by the flushing and cleaning process. The circulating of the composition through the engine can be effected by an external pump or circulation device, or alternatively by circulating the composition as though it were an engine lubricant, e.g., by running the engine and the associated oil pump, typically at “idle” or “fast idle” speed. The term “circulating” includes flushing the engine with the composition, that is, employing one or more passes of the composition through the engine, typically multiple passes.

The time during which the composition is circulated through the engine will depend to some extent on the degree of cleaning that is desired; in most cases the time of circulation should not need to exceed 18 hours. In other embodiments, the time of circulation can be 1 minute to 1 hour, or 2 to 30 minutes, or 5 to 15 minutes.

The temperature of the fluid during the flushing and cleaning operation may likewise be adjusted as desired. If it is circulated by running the engine at a fast idle speed, the fluid may be expected to attain the temperature commonly reached by a lubricant circulated under such conditions. Examples of suitable temperatures include 20-130° C. or 30-100° C. or 40-80° C., which refers to the sump temperature (temperature of the bulk oil in the sump).

After flushing and cleaning of the engine as described above and removal of the composition of the present invention, the engine can be charged with a desired conventional lubricant and returned to service.

EXAMPLES Example 1

A composition is prepared in a mixture of base oils (50% 400 N naphthenic oil and 50% 100 N API Group I oil), having a viscosity at 100° C. of 2.14 mm²/s and 22% aromatic content, 5% of a succinimide dispersant, 1% of a hindered phenolic ester antioxidant, 1.4% overbased calcium and sodium sulfonate detergents, 1.4% zinc dialkyldithiophosphate, 0.4% trialkyl (relatively short chain) borate ester, 0.3% sulfurized olefin antioxidant, 0.1% alkyl sulfone and 10 ppm antifoam agent, all numbers on a diluent oil-free basis.

A 3.8 L six-cylinder gasoline engine is evaluated for high temperature poston deposits by the protocol set forth in ASTM Sequence IIIG Test Procedure Draft 2D prior to the flushing and cleaning of the present invention. Each piston is evaluated at the undercrown, second land, third land, piston skirt, 1^(st) groove, 2^(nd) groove, and 3^(rd) groove positions. The weighted piston deposit result is determined by multiplying each rated area by the following weighting factors: Piston Undercrown 10% 2^(nd) Land 15% 3^(rd) Land 30% Piston Skirts 10% Top Groove  5% 2^(nd) Groove 10% Oil Ring Groove 20%

A total weighted value for each piston is reported on a scale of 0 to 10, with 10 representing an entirely clean piston (higher numbers are better).

The above composition is circulated through the engine by supplying 5.50 L of the composition to the sump of the engine and operating the engine at 1500 r.p.m. for 10 minutes at ambient engine oil temperature (about 50° C.). After the procedure, the engine is drained and again evaluated by the above-described procedure. The results of the evaluation before and after the flushing procedure are set forth in the table below: Weighted Piston Summary Before Flush After Flush Piston 1 total 5.51 5.75 Piston 2 total 4.54 4.50 Piston 3 total 3.56 3.80 Piston 4 total 3.50 3.69 Piston 5 total 5.41 5.61 Piston 6 total 5.58 5.84 Overall piston weighted average 4.68 4.86

The results show that treatment with the composition of the present invention leads to improvement in the cleanliness of the engine as measured by the above test. This improvement in cleanliness is observed even though no volatile or highly flammable solvents are employed in the composition—it is an entirely “lubricant based” cleaner.

Each of the documents referred to above is incorporated herein by reference. Except in the Examples, or where otherwise explicitly indicated, all numerical quantities in this description specifying amounts of materials, reaction conditions, molecular weights, number of carbon atoms, and the like, are to be understood as modified by the word “about.” Unless otherwise indicated, each chemical or composition referred to herein should be interpreted as being a commercial grade material which may contain the isomers, by-products, derivatives, and other such materials which are normally understood to be present in the commercial grade. However, the amount of each chemical component is presented exclusive of any solvent or diluent oil, which may be customarily present in the commercial material, unless otherwise indicated. It is to be understood that the upper and lower amount, range, and ratio limits set forth herein may be independently combined. Similarly, the ranges and amounts for each element of the invention can be used together with ranges or amounts for any of the other elements. As used herein, the expression “consisting essentially of” permits the inclusion of substances that do not materially affect the basic and novel characteristics of the composition under consideration. 

1. A method for removing at least a portion of at least one of sludge, deposits, and wear debris from the lubricated surfaces of an internal combustion engine which has accumulated such sludge, deposits, or wear debris, comprising: (a) supplying to lubricated surfaces of said engine a composition having a kinematic viscosity of about 1 to about 9.3 mm²/s at 100° C. and a flash point of at least about 125° C., comprising (i) oil having at least about 15% aromatics by ASTM D-2007; (ii) at least about 2.5 weight percent of a nitrogen-containing dispersant; and (iii) at least about 0.6 weight percent of an overbased metal detergent; (b) circulating said composition through the engine; and (c) removing said composition from the engine.
 2. The method of claim 1 wherein the composition is circulated through the engine by means of running the engine.
 3. The method of claim 1 wherein the composition is circulated through the engine by means of an external pump.
 4. The method of claim 1 wherein the composition is circulated through the engine for about 1 minute to about 1 hour.
 5. The method of claim 1 wherein the composition is circulated at a temperature of about 20 to about 130° C.
 6. The method of claim 1 wherein the oil is an API Group I base stock.
 7. The method of claim 1 wherein the oil has a viscosity of about 0.5 to about 7.5 mm²/s at 100° C.
 8. The method of claim 1 wherein the dispersant is a succinimide dispersant.
 9. The method of claim 8 wherein the succinimide dispersant has a TBN of less than about 45 and a TAN of greater than about 4, on an oil-free basis.
 10. The method of claim 1 wherein the overbased metal detergent comprises a calcium, magnesium, or sodium sulfonate, phenate, salicylate, salixarate, or saligenin, or mixtures thereof.
 11. The method of claim 1 wherein the overbased metal detergent comprises a sodium sulfonate.
 12. The method of claim 1 wherein the overbased metal detergent component has a TBN of about 100 to about
 800. 13. The method of claim 1 wherein the composition further comprises (iv) at least about 0.5 weight percent of a metal salt of a phosphorus acid.
 14. The method of claim 13 wherein the metal salt of a phosphorus acid is a zinc dihydrocarbyldithiophosphate.
 15. The method of claim 1 wherein the composition further comprises a seal swell agent.
 16. The method of claim 1 wherein the composition further comprises at least one additional additive selected from the group consisting of antioxidants, organic borate esters, and pour point depressants.
 17. The method of claim 1 wherein the composition comprises 0 to about 0.4% polymeric viscosity modifier.
 18. The method of claim 1 wherein the composition is substantially free from polymeric viscosity modifier.
 19. The method of claim 1 wherein the composition is substantially free from solvent having a flash point of less than 93° C.
 20. The method of claim 1 wherein the engine is a gasoline fueled engine or a light duty diesel engine.
 21. A composition having a kinematic viscosity of about 1 to about 9.3 mm²/s at 100° C. and a flash point of at least about 125° C., comprising (a) oil having at least about 15% aromatics by ASTM D-2007; (b) at least about 2.5 weight percent of a succinimide dispersant; and (c) at least about 0.6 weight percent of an overbased metal detergent. 